1. Field of the Invention
This invention relates to a check valve, and more particularly to a spring biased check valve that reacts primarily to fluid flow rather than strictly in response to a pressure gradient across the valve.
2. Description of the Prior Art
Spring biased check valves biased in the open position are well known in the art. Many applications require a valve to close in response to an increased pressure or excessive fluid flow within a fluid device. One such valve is disclosed in FIG. 1 of U.S. Pat. No. 4,874,012. Under low fluid flow conditions a compression spring maintains a valve poppet in a position spaced upstream from an upstream end of the seat body and fluid flow is maintained through a tubular conduit. Upon an increase of fluid flow above a predetermined flow rate, the valve poppet constitutes a restriction and therefore a greater pressure on the upstream side of the valve poppet over the downstream side thereof overcomes the biasing action of the spring and the poppet valve shifts to close the valve. However, this conventional design has limited applications.
In order to create a sufficient pressure gradient, the poppet valve head must be dimensioned within the tubular conduit to create a restriction in the fluid flow. As more fluid is forced through the conduit, the restriction induces the necessary pressure gradient to overcome the bias of the spring and close the valve. Thus the size of the valve head in relation to the tubular conduit in which the fluid flows is limited if not predetermined. If the valve head is too small relative to the conduit and there exists a significant space between the components, sufficient pressure gradient will not be induced and the valve will not close. Conversely, if the valve head is too large, the amount of fluid allowed to flow through the conduit will diminish defeating the ability to permit flow in an opened position. Thus the size of the valve head is strictly dependent on the dimensions of the surrounding space in which the fluid flows. A valve head of any other dimension will yield an unworkable device. Such check valves of the prior art will not work if simply installed in a wall having a significant area. If such a valve were placed on a larger wall surface area, no matter what level the pressure reached within the reservoir body, the valve would not close, as the geometry does not provide the required restriction to induce the pressure gradient across the valve head. Thus these prior art devices do not provide the ability to retrofit a reservoir with a generic valve assembly by simply installing a valve through a wall surface of generic geometry.